Most played cards in Madness:

5 Decks
Hollow One
20 copies - 4 average
Vengevine
20 copies - 4 average
Blazing Rootwalla
20 copies - 4 average
Basking Rootwalla
20 copies - 4 average
Lion's Eye Diamond
20 copies - 4 average
Anje's Ravager
20 copies - 4 average
Faithless Looting
20 copies - 4 average
Street Wraith
16 copies - 3.2 average
Burning Inquiry
16 copies - 3.2 average
Putrid Imp
16 copies - 3.2 average
Wooded Foothills
15 copies - 3 average
Firestorm
14 copies - 2.8 average
Ancient Grudge
14 copies - 2.8 average
Badlands
13 copies - 2.6 average
Anger
12 copies - 2.4 average
Bloodstained Mire
12 copies - 2.4 average
Faerie Macabre
11 copies - 2.2 average
Taiga
9 copies - 1.8 average
Leyline of the Void
8 copies - 1.6 average
Mindbreak Trap
6 copies - 1.2 average